Sonos Five Line in

Anything is possible. Have you submitted a diagnostic, and contacted Sonos support about it?

No, chatting with them would be fine, I’d think, although I’ll admit that in some similar situations, I’ve called other support lines multiple times, in order to speak with a rep that actually understands what I’m calling about, and isn’t just reading from a script. I’d have to imagine that Sonos folks have varying levels of knowledge, although the two times I have called in, the service has been excellent. 

It could be something as simple as some dirt in the line in, or a bad solder, or any of many more physical things that may not show up on a diagnostic. Unlikely, although not completely impossible, to be a software issue, although I’d think if that was a possibility, there would be hundreds of posts about it. 

But this community has no control, only guesses that can be given to you. We can’t force your system to work by our assumptions, nor can we force Sonos to swap out your unit.